Mechanical time fuse



March 7, 1939. 'v

E. H. SCHENK MECHANICAL TIME FUSE Filed Sepi. .25, 1935 I I I INVENTOR.Patented Mar. 7, 1939 UNITED STATES PATENT OFFICE by direct and mesneBrandt, Paris, France assignments, to Edgar Application September 25,1935, Serial No. 41,990 '9 01. 102-436) This invention relates. to amechanical time fuse for artillery projectiles, and more especially to amechanical time fuse of the type in which the hollow. body of the fuseis formed by a fixed base and an adjustable setting cap and in which arotary timing member, controlling the release of a trigger and hammermechanism; is set in angular position before the fire by means of, ,thesetting cap and is driven during the flight of the projectile inopposite direction by a spring motor at a speed governed by means of aclock mechanism. i

In fuses of this type, the rotary timing member is usually a very lightand frail disc, ring or arm, which may be easily unset, deformed orbroken by the shock of discharge of the gun and considerabledifficulties are encountered in practice to couple this member to thesetting cap so that no unsetting of the fuse may occur during the 0firing operation.

Further one usually finds in these fuses a stop which limits the angulardisplacement of either the setting cap or the timing member and means toprevent the rotation of the setting cap in the wrong direction. Allthese organs are fragile and grave accidents may occur if one of them isbroken during the setting operation or in the bore of the gun.

Moreover, in all known fuses of this type, as

0 the clock mechanism of the fuse is housed in a casing fixed to thebase, it is impossible to utilize for the moving parts of the fuse, allthe free space inside the body.

The object of the present invention is to realize 5 a mechanical timefuse of the type'referred to which will obviate all these difiicultles,which will be cheaper, lighter, smaller in diameter and better adaptedto mass production than the known fuses of this type, which will have alower center of gravity and a much better dynamic balance;

in which there is a more rational utilization of the free space insidethe body of the fuse, a much more powerful motor and a positive couplingbetween the base and the setting cap directly after the settingoperation and between the setting capand the timing member before andduring firing; which will be perfectly safe in handling and in the boreand stable in storage and which can be set either way from 0.5 to 100seconds.

0 The main feature of my invention through which this object is attainedis the use of acompound organ-that I will hereinafter designatethroughout the description and the claims as the rotor", for lack of abetter term-housing the 5 clock mechanism of the fuse and acting astiming organ, as mainshaft, as eccentric organ of transmission betweenthe motor and said clock mechanism and as means to control the releaseof the trigger mechanism of the fuse.

Other features of my invention are the pro- 5 vision of means forcoupling positively the setting cap to the base, not upon the firing-asit is done in all known fuses of this type-but already at the end of thesetting operation of the fuse, for holding the rotor positively coupledrespectively to the setting cap before firing and to the base during thepositive acceleration of the projectile; for absorbing the shock ofdischarge of the gun,

for arming both the mainspring and the percussion spring by inertia atthe time of the firing; for protecting and adjusting the hairspring ofthe clock mechanism; for journaling the rotor in the axis of the fuse sothat the friction be reduced to a minimum. and the provision of anauxiliary locking device for the trigger mechanism of the fuse, whichpermits to set the fuse in either direction and to do away altogetherwith the usual stops limiting the angular displacement of the settingcap.

With the foregoing and other objects in view which will appear as thedescription proceeds, my invention consists in the novel use in amechanical fuse of a rotor housing the clock mechanism of the fuse andacting as the timing member and the mainshaft. of the fuse, as aneccentric organ of transmission between the motor of the fuse and thetrain of said clock mechanism during the flight of the projectile and asthe actual means controlling the release of the trigger mechanism of thefuse at the time set for the burst of the projectile, as well as in thenovel arrangement and combination of parts and in the details ofconstruction hereinafter described and claimed, it being understood thatchanges in the precise embodiment of the invention herein disclosed maybe made within the scope of what is claimed without departing from thespirit of the inven- 1 tion.

For convenience of illustration and explanation,

I have shown my present invention as applied to a mechanical fuse havinga spring motor and a timing and release mechanism of essentially thetype and character of that disclosed in my pendfuse, showing the movingparts of the fuse in their normal position of rest; l I Figure 21s atransversal sectionmadeon line B- -BofFigure 1; I a I Figure 3 is anelevation, showing, a detached part of this fuse at a reduced scale;Figure 4 is a transversal section made on line i C- C of Figure l andshown also at a reduced scale, and

. Figure shows a modification of the auiriliary I locking device; I

* In this drawing, lrepresentsthe base of the fuse; 2 the usual settingslot. for engagement with a correspondingpawland lug of the setter and 3I the usual scalegraduated in seconds and located on the upper edge ofsaid base. I

' According-to one feature of my invention, in-- I steadofbeing-markeddirectly on said edge, this scale is marked on a steel bandfastened on this, 'upperedgeby any suitable means, forinstance byhaving. a portion of this band clamped (as shown Figure l) in thesetting slot'2 and provided with an inside projecting rim or flange 3A,cutso as to form acircular series of sharp steel I a points, convergingtoward the center of thefuse.

4 indicates thesetting cap, or brass cap, which is .rotatably mountedinto the base i and held against axial displacement in relation tosaidbase by means of three set screws or shoulder screws 40, working in acircular groove 4!.

setting cap is likewise provided with theusuai;

setting slot 5 andwith a steel band 6 fastened on 7 its. loweredgeand-on which is marked the usual index (not shown). This band is flushwith the:

. graduated band :3 and is provided, as this latter,

. with an inner projecting flange 6A, cut so as to form a circularseries of sharpsteel points. Be-

hind the bands 3 and 6 is out, half in the setting cap 4 and half in thebase I, an annular groove Ill, while a ring or washer H of soft metal,for instance of lead, is loosely mounted between said cap 4 and base I,opposite the steel points 3A and 6A. 7

These parts 3, 3A, 6, 6A and II cooperate at the time of the setting ofthe fuse to couple positively the setting cap 4 to the base I as soon asthis setting is performed and that, while the projectile is still in thesetter. This is preferably accomplished automatically by means of a pairof diametrically opposed eccentrics, wedges or cams forming parts of therelease mechanism of the setter, which crush the bands 3, 6 in twodiametrically opposed places so that some of the steel points 3A, 6A arepermanently empaled in the lead washer II.

1 shows the nose cap of the fuse which may be set in angular positionand clamped in this position in the eye of the setting cap 4 by means ofa set screw 38, provided with a conical end which acts as a wedge in acircular groove 39. Thus assembled, the base I, setting cap 4 and nosecap 1 form the hollow body of the fuse.

An annular plate 8 is fastened internally to the setting cap 4 by meansof screws 24. This plate supports a compression flat volute spring 9,the lower coil of which is secured in a circular recess of said plate,while its upper coil is fixed in an opposite circular recess provided ina ratchet ring l0, having radial ratchet teeth ll. l2 indicates a massor weight which is used to compress the mainspring 9 by its setback uponmainshaft l6.

the firing of the projectile; This weight is freely mounted in thesetting cap between the ratchet ring "I, upon which it rests, and ashoulder of the I setting cap;

l3 represents a sleeve, the top part of which is split so as to form acircular series of resilient hooks. The lower part of this sleevecarries a washer provided with four springs or flaps l5,

which are normally engaged under the inner" edge'of the plate '8 so asto prevent the accidental 'slidingof the ring I t'along ashaft I 6,arranged in the axis of the fuse and constituting the mainshaft thereof.

Thisdriving shaft'is provided with a head '11,

forming the lower race of a ball thrust bearing 18, held'in place bymeans of a cylindrical casing are symmetrically cut into the peripheryof the screwed into'the reinforced base of the sleeve l3 and providedeach with a conical end which constitutesthe rotor defined in thestatement of cation. All the moving parts'of' theclock-mecm anism of thefuse, that is, the train, the escape mechanism, the balance and thehairspring are lodged inside this rotor.

22 and25 are, respectively, the first pinion and the flrst wheel of thistrain, while 26'indicates the last pinion thereof and 21 the escapewheel,

which oooperates'with a cylinder 28, fastened on top end 32 of thisspindle carries a staff 33eto which is secured-the lowerend of thehairspring 34 of the fuse. This latter is of'the straight or torsiontype used in the galvanometers and is held straight by a steel tube 31,while its upper end is engaged in a narrow slot 3| provided in the nosecap I so as to be prevented from turning before the fire but free toexpand axially by dilatation.

The inner cylindrical surface of .the steel tube 31 is very smooth so asto reduce the friction to a minimum. The upper staff 35 of thehairspring is loosely mounted in a cylindrical groove provided in theinner periphery of a split set grub screw 36, which may be adjustedalong the inner threaded part 31A of the steel tube 31 so as to adjustthe operative length of the hairspring.

The planetary pinion 22 is in constant mesh with an annular gear 23,freely mounted in the rotor 2| but coupled to the setting cap 4 by meansof four semi-circular ears 23A (Figure 3), working in four correspondinglongitudinal keyways 42A provided in the inside periphery of the settingcap 4. The cylindrical rotor 2| is slidably mounted in a correspondingbore of the setting cap 4, but is normally coupled to said can by meansof four balls 42, lodged partly in four corresponding spherical socketsprovided in the outside periphery of the rotor 2| and partly in the 20indicates a pair of spurs 7 l4, freely mounted in the eye of the settingcap I 4between the nose cap '1 and the weight I2;

Two helical grooves l9 with progressive pitch invention at the beginningof the present'specifi- I the spindle-30 0f the balance 29 of the fuse.The 1 The cylindrical rotor 2| is journalled in the axis of the fuseinside the cap 4 on twoball thrust bearings: the upper bearing|8,'already mentioned, and a lower one 44, the lower race of which 45leans upon thepercussion spring 46 so as to act as a shock absorberduring the acceleration. Upon the firing of the projectile, the rotor 2|sets back by inertia until this lower race 45 meets the upper edge of acylindrical guide 48, carrying a firing pin 41, while the bottom of therotor 2| is empaled on four steel points 63, carried by a cylindricalinner. projection IA of the base I.

The coupling balls 42 are thus brought opposite the radial holes 43 andare then free to escape under the action of the centrifugal forcedeveloped by the spin of the projectile, thus uncoupling the rotor 2|from the setting cap 4 at .the beginning of the positive acceleration ofthe projectile, but this rotor 2| is then momentarily coupled to thebase I and thus prevented from turning, until the end of this positiveac-' celeration, by the steel points 63.

The weight I2 sets back simultaneously with the rotor 2| during thisacceleration, thus compressing the mainspring 9, while the casing 2|, byits setback compresses the percussion spring 46.

The casing 14 of the ball bearing I8 is provided with a periphericgroove 15, in which are lodged three centrifugal segments I5 (Figure 2),which expand under the action of the centrifugal force as soon asnearthe end of the setback of the casing |4this groove registers with ashoulder. ll, provided in the setting-mp4.

'49 indicates a cylindrical bore cut in the -cyring 53 is rotatablymounted in a larger holding ring 58, which is secured to the base I byany suitable fastening means such as a screw or a key (not shown).

A circular groove 13 (Figure 4) is cut in the base I directly under thering 53, while a screw 53B is screwed into said ring 53 and projectsthereunder into said grow/e13. A spring I2 is normally compressed in thegroove 13 between one end of this groove and the projection of the screw533, thus tending to rotate the release ring 53 in the direction of thearrow shown in Figure 4, but this ringis normally prevented from turningeither way by means of a bar 54, freely mounted in a slot 5'|, cut partin the base part in the holding ring 58 and part in the release ring 53.The lower end of this bar is "guided in a longitudinal keyway 56, outparallel to the axis of the fuse also part in the base I, part in theholding ring 58 and part in the release ring 53, by means of a fulcrumor trunnion 55, projecting on both sides of the bar 54, while the upperend of this bar is provided with a lateral projection 54A, which isengaged in a circular path or groove 6|, formed in the bottom of therotor 2|. The opposite side of this upperend 'of the bar 54 penetratesinto a release notch 59, out into an annular rim or projecting edge 6|]of this bottom of the rotor 2|, at

the end of the trajectory of the projectile. Normally, i. e., until thefuse is set, the bar 54 is held in the position shownin Figure 1 by aninwardly projecting lug 62, seclifed to the lower edge of the settingcap 4,- and constituting the auxiliary locking device defined in .thestatement of invention.

This lug 62, the release notch 59, and theslot 51 have the same widthand are slightly wider than the bar 54. -This rim constitutes at thesame time the timing ring of the fuse and the main locking member orrotary organ controlling the release of the firing pin 41.

64 shows the primer-plunger of the fuse, which is slidably mounted inthe cylindrical bore 66 of the base I, while 65 indicates the usualdetonator screwed into said base I. The plunger 64 is normally held backagainst the detonator 65 in the usual way by means of two centrifugalbolts 61. kept themselves in operative position by means ofv two inertiapins 63, submitted to the action ofsprings69. This plunger is still heldback during the flight of the projectile, i. e.-, after having beenreleased by the disappearance of the bolts 61 under the action of thecentrifugal force, so as to be prevented from creeping towards thefiring pin 41,

by any suitable known means (not shown) such as a creep spring or ashear-pin.

I The operation of the fuse is as follows:

Normally, i. e., before the setting, the movable parts of the fuse arein the position shown in the storage as the mainspring 9 and thepercussion spring 46 are then uncompressed.

Whenthe fuse is set, the setting cap 4 and the rotor, 2|,positively-coupled to this c'ap by the coupling balls 42, are solidarilyrotated to the desired angular position, in accordance with the fuserange data, by the fuse setter pawls engaging the slots: and 5 of,respectively, the base and the n During the setting-operation the head54A of the release lever 54 slides in the groove 6|, while 4 thisrelease bar 54 is heldin its operative position by the inner peripheryof the annular rim 60, which enters in action as soon as the lug 62releases this bar. As soon as the setting is performed, a pair ofdiametrically opposed cams or eccentrics forming part of the releasemechanism of the setter, squeeze or crush the bands 3 and 6 in twodiametrically opposed places so that some of the steel points 3A and 6Aare empaled in the lead washer 1|. .The'setting cap 4 is thus positivelycoupled to the fixed base I as the band 3 is fastened to this latter,,while the band 6 is fixed to the former and the release notch 59 istherefore immobilized in its set angular position, which determines theduration of the flight of the projectile.

Upon the firing of the projectile, the rotor 2| sets back by inertiaagainst the action of the percussion spring 46 until the race 45, actingas a shock absorber, meets the top of the firing pin plunger 48, whilethe ears 23A of the internal gear 23 slide in the keyways' 42A,thebottom of pushed back parallel to itself as its lower end is guidedby the sliding of the fulcrum Ii in the keyway it, while its upper endremains confined between the rim'il and the groove therefore preventingany accidental release of the release ring 52.

The rotor 2| is also followed in its setback by the casing 14, theweight l2 and the ratchet ring In. These latter I continue their ownsetbacks after that of the rotor has been stopped until the conical partof the ratchetring it meets the heads of the hooks l4 and push themslightly to wards the axis of the fuse until they snap above thisconical part, but the former is stopped when its bottom empales on thesteel points 63. In this back position, the centrifugal segments 16expand under the action of the centrifugal force in the bore of largerdiameter formed under the shoulder 11 (as shown in dotted lines Figure'2).

Simultaneously with the setback of the rotor 2|, the percussion orimpact device of the fuse is armed by the setback of the inertia pins 68and the radial displacement of the bolts 61 under the action of thecentrifugal force.

Near the end of the positive acceleration, the force of inertia acting,on one hand, upon the casing 14, the rotor 2| and the percussion spring46, and, on the other hand, upon the weight l2, the ratchet ring l0 andthe mainspring 9, is

counterbalanced and immediately' afterwardsovercome by the energy storedin said springs 46 and 9 and the rotor 2| is, therefore thrust away fromthe steel points 63 until the segments 16 come to abut against theshoulder 11. As the hooks l4 are thus stopped while the mainspring 9continues to push the ratchet ring |0 forward: first, a positiveengagement is created between these books i4 and the teeth thuspreventing the sleeve l3 from turning, and, second, a straight force,parallel to the axis of the fuse and tending to pull this sleeve towardthe nose of the fuse, is thus applied upon this sleeve.

Were it not for th s engagementof the hooks l4 in the ratchet teeth I I,this sleeve l3 would then be spirally wound upon the mainshaft it underthis pulling action of the mainspring 9, but as it v is therebyprevented from turning, this straight pulling force is transformed bythe spurs 20, engaged in the helical grooves l9, into a torque, underthe action of which the rotor 2| starts to rotate upon itself on theball thrust bearings l8 and 44. This rotation is facilitated by the factthat-save the friction of the keyways 42A against the ears 23A of theinternal gear 23there exists no friction between the mainshaft it,together with the solidary rotor 2 l, and the hollow body of the fuseformed by the base and the setting cap 4.

As the pitch or thread of the helical groove I9 is progressive, theincrease in leverage thus obtained compensates for the diminishingpulling force of the mainspring 9' andv the value of the torque appliedon the mainshaft I6 remains practically constant during the whole flightof the projectile, in spite of the fact that the mainspring losesprogressively its energy. During all of its forward movement under thepulling action of the mainspring, the ratchet ring In is guided alongthe bore of the setting cap by the periphery of the we ght l2. Theangular speed of the rotor thus driven by the main spring 9 is regulatedby the action of the hairspring 34 cooperating with the balance 29 andthe cylinder 28 to check the rotation of the escape wheel 21, to whichis transmitted the motive force throughthe train 28, 29,

the planetary pinion 22 and the fixed internal gear 22.

The release notch 59 is thus brought back in its initial positionopposite the release bar 54. As the lug 82 or auxiliary locking memberdoes no more interfere with the release mechanism, the upper end of thisbar is now free to rock about the fulcrum 55 in the slot 51 under theaction of the centrifugal force and to enter into said notch 59. Thisfrees the ring 53, which rotates under the action of the spring 12 inthe direction of the arrow of Figure 4, thus releasing the locking ballswhich then, under centrifugal action and considerable leverage or sidepressure from the firing-pin plunger 48, enter into the circular notches53A, thus releasing the firing-pin plunger 48 practically at the instantthe upper end of the'bar 5 enters into the release notch 59.

Driven by the percussion spring 46-in which has been stored the energyof the shock absorbed during, the acceleration of the projectile,-thefiring-pin 41 then strikes the primer 64, which detonates the detonator65 and finally the bursting charge in the projectile.

If, during the flight of the projectile, the nose cap 1 meets anobstacle, or on impact on the ground, if the time mechanism of the fusehas rotor 2|, is made when the manufacture of the fuse is completed,before mounting the nose cap 1 into the eye of the body 4, by means of aspecial tool, which permits the screwing or u'hscrewing of the grubscrew 36 in the threaded part 31A of the tube 31, wh le at the same timepreventing the rotation of the upper end of the hairspring 34. Then thenose cap 1 is mounted on the setting cap 4 and this upper end of thehairspring 34 is coupled thereto by its engagement into the slot 3|thereof. It becomes thus pomble to adjust the angular position of thehairspring and the relative angular position of the cylinder 29 withrespect to the escape wheel 21- or to provide a preliminary torsion ofthe hairspringby merely rotating the nose cap 1 and clamping it in thedesired position by means of the set screw 38. The staff 35 is mountedinthe split end of the screw 36 with enough friction to hold the upper endof the hairspring 34 in its adjusted position, even after this upper endhas been separated from the nose cap 1 by the setback of the rotor 2|and also during the entire flight of the projectile, in spite of thealternative torsion given either way to the hairspring by theoscillations of the balance wheel.

Instead of utilizing forthe auxiliary locking member the fact that thesetting cap 4 is immobilized during the angular return movement of therotor 2|, after having accompanied this latter in its angulardisplacement during the setting of the fuse, one could utilize an organ,which will accompany the rotor in its axial setback, but wfll be axiallyimmobilized at the end of the acceleration, while the rotor rebounds axially forward under the combined action of the springs 9 and 49.

An example of such a modification is shown in Figure 5, in which thisorgan replacing the lug 62- as an auxiliary locking member is therelease bar 54 itself.

above the rim 6!! and the release notch 59. The upper end of the releasebar 54 is normally engaged in said groove and is locked in this positionby a spring 18, normally engaged in a lower notch 54B of the bar 54, sothat the bar 54 acts then as a tie or stay to prop the rotor in itsuppermost position. When this bar is pushed down by the setback of therotor 2|, this spring 18 snaps in an upper notch 54C at the end ofthetravel of the bar and locks this latter in its lowermost position.Thus, this bar cannot follow the rotor when .it rebounds forward underthe action of the springs 9 and I6 and, therefore, the upper end of thebar is kept behind the rim outside the groove BIA at the level oftherelease notch 59 ready to rock under the action of.

The setting cap is positively coupled to the base before firing and thetiming ring 60 is positively coupled to the setting cap before andduring firing, thus avoiding all the defects and risks of the couplingdevices of the known fuses of this type, which operate by inertia orcentrifugal action only at the time of firing.

Due to the auxiliary locking device and the absence of stop or stops tolimit the angular adjustment of the setting cap, this latter may be seteither way, even of exactly 360 degrees with perfect safety. I

Due to the suppression of the usual fixed casing for the clockwork, thesize of the movement of the fuse may be made smaller in diameter, so asto beadaptable to a larger number of projectiles of different caliber orprofile, without having to reduce the accuracy of the setting beyond theaccepted limits. The weight of this movement is, therefore, considerablyreduced. For instance, the weight of the movement of the fuse shown inthe drawing will be abcut 80 gr.,

which compares with a corresponding weight of f 200 gr. at least for themovement of most of the known mechanical fuses of this type.

There is a considerable-reduction in the number of parts and the wholefuse has been carefully designed so as to be cheaper to manufacture .andespecially well adapted to mass production.

Due to the lowering of the center of gravity of the fuse, and to theaction of the ball bearingslB, 44 and of the 4 locking balls 5|, a muchbetter dynamic balance exists than in the known mechanical fuses.

As the worst of the shock of discharge is absorbed by the percussionspring, it becomes possible to use more delicateand therefore moreeificientgoverning means for the clockwork, for instance, it becomespossibleto use a cylinder escapement.

Due to the lightness of the bar 54, there isvery little friction on themovement of the fuse due to the release mechanism.

As the springs 9 and 46 are normally uncompressed, the fuse may bestored for very long periods without losing any part of its efiiciency;

In this modification, the annular groove BIA is cut in the bottom of therotor H The adjustment of the operative length of the hairspring may bemade on a. much larger range than in any known mechanical fuses. It thusbecomes possible to allow for liberal plays or.

variations in the weight or equilibrium of the balance masses. 1

The different parts of the movement are standard for all types ofdifferent duration of this fuse, except the balance, the hairspring, andthe bands 3, 6. For instance, a'20 seconds type will be made of exactlythe same parts than a 100 seconds type, save that'the hairspring and themasses of the balance will be made much heavier.

What I claim and desire to secure Patent is:

1-. Ina clockwork operated mechanical fuse: an adjustable setting cap, acompressionma'inspring normally uncompressed and arranged in the axis ofsaid cap, a set back weight axially slidable in by Letters said cap. tocompress this mainspringuduring the positive acceleration-of theprojectile, means to transform the straight force'thus stored in themainspring into a torque, a mainshaft pivoted in the axis of thismainspring and directly submitted to the action of this torque duringthe flight of the projectile, a'clockwork casing pivotally and slidablymounted in this cap, a cylindrical cover for this casing made in onepiece with this mainshaft and eccentric means of transmission carried bythis cover and comprising a non-rotatable internal gear freely mountedin this cover, a planetary pinion driven by said internal gear anddriving the train of the clockwork of the fuse and means to couplepermanently this internal'gear to the setting cap.

2. A mechanical fuse as claimed in claim 1, in which the means to couplepermanently the internal gear to the setting cap comprises at least alongitudinal keyway provided in the inside periphery of the setting capand at least a corresponding lug formed on the periphery of the internalgear and projecting intosaid keyway so as to act as a slidable key tohold the internal gear constantly coupledto the setting cap.

3. In a mechanical fuse: a hollow body formed of a fixed base and anadjustable setting cap, a rotor rotatably and slidably mounted in saidbody, a firing pin plunger axially slidable in-said base, locking ballsnormally holding this plunger in the inoperative position of the firingpin, and a trigger mechanism to unlock these balls at the end of thetrajectory of the fuse, said trigger mecha nism comprising a shiftablelocking ring rotatably mounted in the base of the fuse, and normallyholding the, locking balls in their operative position, release notchesprovided in the inner periphery of said ring, a spring tending to shiftthis ring so that said' release notchescome to register with the lockingballs and thus release the firing pin plunger at the end of thetrajectory, a

radial notch provided in the outer periphery of locking means normallyholding said plunger in the inoperative position of the firing pin, atrig-- 'ger mechanism to unlock said locking means, a notched circularrim formed at'the bottom of the,

rotor to lock the trigger mechanism in its active position after thesetting operation of the fuse, a continuous circular groove provided inthe bottom of the rotor above the level of the notched rim thereof, ashiftable bar provided with two lateral-notches andhaving its upper endengaged respectively into said groove before the fire and behind thenotched rim of the rotor during the flight of the projectile and a flatspring carried by the base of the fuse and cooperating with either ofthese notches to hold this bar in either of these two positions. A

5. In a mechanical fuse: a hollow body formed of a fixedlbase, anadjustable setting cap, held to said base and an adjustable nose capheld to said setting cap, a rotor journaled on ball bearings and axiallyslidable in said body, a clockwork comprising a train, escape mechanismand balance wheel which are lodged in said rotor, a cylindrical coverfastened to said rotor, a, hollow mainshaft made in one piece with thiscover, a straight torsion fiat hairspring axially arranged in thismainshaft, means to adjust the operative length of this hairspring, areleasable coupling between the top end of this hairspring and said nosecap to allow for angular adjustment of the hairsiaring before the fireby turning said nose cap and means to lock said nose cap in thedesiredangular position.

.6. In a mechanical fuse as claimed in claim a steel tube with aperfectly smooth inner periphery secured in the hollow mainshaft toprotect the hairspring and house the means for adjusting the lengththereof.

'7. In a mechanical fuse for artillery projectiles; a hollow fuse bodyformed of a fixed base and an 'angularly adjustable setting cap axiallyheld to said base, longitudinal keyways provided in the inside peripheryof this setting cap,- a spring-- driven setback rotor pivotally andslidably mounted in the axis of said setting cap, a clockwork entirelylodged in this rotor to govern the angular speed thereof,releasable'coupling means slidably mounted in said keyways andcontrolled by the setback of this rotor, said means being normallyrying-said releasable coupling means, the latter being constituted by atleast one coupling ball, and at least one radial bore provided in saidsetting cap below said longitudinal k'eyways and into which saidcoupling ball escapes under centrifugal action for uncoupling said rotorfrom said setting cap after the firing.

9. In a mechanical fuse: a hollow fuse body formed of a fixed base andan angularly adjustable setting cap axially held to said base, adjacentgrooved edges on both the base and the setting cap, a graduateddeformable steel band secured on the upper grooved edge of the base, anindexed deformable steel band secured on the lower grooved edge of thesetting cap, steel points carried by both of these bands and radiallyprojecting toward the center of the fuse and a lead washer interposedbetween the base and the setting cap opposite these steel points.

EDOUARD H. SCHENK.

